INVESTIGADORES
CASTRO Marcela Paola
congresos y reuniones científicas
Título:
MIXED STARTER CULTURES FROM AUTOCHTHONOUS STRAINS IN FERMENTED MEAT PRODUCT MODEL SYSTEMS
Autor/es:
N.Z. PALAVECINO; RIVAS, FRANCO P.; CASTRO M.; GARRO O.A.; VIGNOLO G.M.
Lugar:
S.M. de Tucumán
Reunión:
Simposio; IV Simposio Internacional de Bacterias Lácticas; 2013
Institución organizadora:
CERELA-CONICET
Resumen:
The introduction of starter cultures designed using autochthonous
microflora can enhance safety of fermented meat products while preserving their
sensory qualities. The selection of potential starter strains is based on their
technological and safety characteristics. Each of the strains of a mixed
culture meant to be added to a meat product should be compatible. A first
approach to this situation can be simulated in model systems where assessments
compiled in vitro can be checked. Hence,
the aim of this study was to evaluate the behavior of pre-selected
autochthonous strains, as mixed cultures, in meat model systems. From a compatibility
trial, carried out by means of the agar well diffusion method, comprising seven
strains of Lactobacillus sakei and
three strains of coagulase negative cocci (CNC) (Staphylococcus vitulus and two S.
xylosus strains), two pairs of
strains were selected. Culture A: L.
sakei 487 and S. vitulinus; culture
B: L.sakei 442 and S xylosus C8. The meat model contained: minced
beef and pork meat (70:30), NaCl, milk powder, sugar, spices and KNO3.
The ingredients were thoroughly mixed and placed in a beaker. The meat matrix
was separated into three batches, which were then subdivided into six batches
to create the corresponding duplicates. Batches A and B corresponded to the
aforementioned mixed cultures and the third one corresponded to the control
system, with the addition of sodium azide and no added cultures. The batches
were incubated at 20°C and samples were withdrawn at the beginning of the
trial, one and seven days after inoculation. Microbial counts were assessed on
MRS agar and mannitol salt agar (AMS). Total protein content on sarcoplasmic
fraction was determined by means of the bicinchoninic acid method and free
aminoacid concentration was determined by the OPA method. pH measurements were
also registered. Both mixed cultures adapted well to the meat environment; LAB final
counts reached values of 8.6 and 8.8 log colony forming units per gram (cfu/g) and
CNC final counts were 7.4 and 8.3 log (cfu/g)
in batch A and B, respectively. Regarding pH values, they diminished
from 5.54 (initial time) to 4.66 (A) and 4.68 (B) at the end of the trial,
while the control system did not show pH variations. Final pH values from both
batches are similar to those found in local dry sausages at the end of the
ripening stage. Total protein content reduction was 16% (control), 77.9% (A)
and 78.4% (B) indicating a strong metabolic activity of both mixed cultures.
Besides, the release of soluble aminoacids started being 0.98 mMl, showed a
peak of 3.11 mM (A) and 2.43 mM (B) at 24 h, followed by a reduction (1.99 mM)
in both batches. Protein fraction released at 24 h may have contributed to
aminoacid supply for bacterial growth. The acidogenic capacity and the
hydrolysis of meat proteins observed in batches A and B highlight the potential
contribution of both mixed cultures to meat fermentation.